thomson

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Slide2: 

A Few Facts about our friend Mr. Thomson… Born Joseph John Thomson December 18th 1856 - August 30th, 1940 Attended University of Manchester where he studied engineering, mathematics, physics and chemistry Planned to be an engineer, but his dream was to carry out his own research 1890 - Married Rose Paget, daughter of a physics professor at Cambridge 1906 - Awarded the Nobel Prize for Physics because of his investigations of the passage of electricity through gases Taught Ernest Rutherford Had 2 kids, George and Joan 1937 - His son, George, was awarded the Nobel Prize for Physics

A Model of the Atom: 

A Model of the Atom J.J.Thomson knew from experiments that atoms contained negative as well as positive particles. But atoms are neutral, that is, have no net charge. So atoms must contain equal numbers of positive particles (PROTONS)+ and negative particles (ELECTRONS)-- . In 1907 Thomson proposed the model that inside an atom there was a mixture of equal numbers of protons and electrons, scattered randomly around, just as raisins and currants are found inside a plum pudding.

Experiments!? You bet!: 

Experiments!? You bet! J.J. Thomson suggested that atoms have different parts. He came up with the idea that cathode rays are really streams of very small pieces of atoms. Three experiments led him to this… Cathode Ray - A stream of electrons emitted by the cathode in electrical discharge tubes Cathode - the electrode or terminal by which current leaves an electrolytic cell, voltaic cell, battery, etc

Experiment 1!: 

Experiment 1! Thomson built a cathode ray tube ending in a pair of metal cylinders with a slit in them. These cylinders were in turn connected to an electrometer, a device for catching and measuring electrical charge. Perrin had found that cathode rays deposited an electric charge. Thomson wanted to see if, by bending the rays with a magnet, he could separate the charge from the rays. He found that when the rays entered the slit in the cylinders, the electrometer measured a large amount of negative charge. The electrometer did not register much electric charge if the rays were bent so they would not enter the slit. As Thomson saw it, the negative charge and the cathode rays must somehow be stuck together: you cannot separate the charge from the rays

Experiment 2!!: 

Experiment 2!! When physicists tried to bend cathode rays with an electric field. Now Thomson thought of a new approach. A charged particle will normally curve as it moves through an electric field, but not if it is surrounded by a conductor. Thomson suspected that the traces of gas remaining in the tube were being turned into an electrical conductor by the cathode rays themselves. To test this idea, he took great pains to extract nearly all of the gas from a tube, and found that now the cathode rays did bend in an electric field after all.

Experiment 3!!!: 

Experiment 3!!! Thomson’s third experiment sought to determine the basic properties of the particles. Although he couldn't measure directly the mass or the electric charge of such a particle, he could measure how much the rays were bent by a magnetic field, and how much energy they carried. From this data he could calculate the ratio of the mass of a particle to its electric charge (m/e). He collected data using a variety of tubes and using different gases.

Slide8: 

the hypothesis that Thomson came up was.. "we have in the cathode rays matter in a new state, a state in which the subdivision of matter is carried very much further than in the ordinary gaseous state: a state in which all matter... is of one and the same kind; this matter being the substance from which all the chemical elements are built up." Hypothesis/Conclusion

Slide9: 

Bibliography http://web.lemoyne.edu/~giunta/thomson1897.html http://www.britannica.com/nobel/micro/591_84.html http://www.bath.ac.uk/ncuacs/rslp-jjt.htm http://www.answers.com/topic/j-j-thomson